--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/spandsp-0.0.3/spandsp-0.0.3/src/spandsp/dtmf.h	Fri Jun 25 16:00:21 2010 +0200
@@ -0,0 +1,213 @@
+/*
+ * SpanDSP - a series of DSP components for telephony
+ *
+ * dtmf.h - 
+ *
+ * Written by Steve Underwood <steveu@coppice.org>
+ *
+ * Copyright (C) 2001, 2005 Steve Underwood
+ *
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ * $Id: dtmf.h,v 1.5 2006/10/24 13:45:28 steveu Exp $
+ */
+
+#if !defined(_DTMF_H_)
+#define _DTMF_H_
+
+/*! \page dtmf_rx_page DTMF receiver
+\section dtmf_rx_page_sec_1 What does it do?
+The DTMF receiver detects the standard DTMF digits. It is compliant with
+ITU-T Q.23, ITU-T Q.24, and the local DTMF specifications of most administrations.
+Its passes the test suites. It also scores *very* well on the standard
+talk-off tests. 
+
+The current design uses floating point extensively. It is not tolerant of DC.
+It is expected that a DC restore stage will be placed before the DTMF detector.
+Unless the dial tone filter is switched on, the detector has poor tolerance
+of dial tone. Whether this matter depends on your application. If you are using
+the detector in an IVR application you will need proper echo cancellation to
+get good performance in the presence of speech prompts, so dial tone will not
+exist. If you do need good dial tone tolerance, a dial tone filter can be
+enabled in the detector.
+
+\section dtmf_rx_page_sec_2 How does it work?
+Like most other DSP based DTMF detector's, this one uses the Goertzel algorithm
+to look for the DTMF tones. What makes each detector design different is just how
+that algorithm is used.
+
+Basic DTMF specs:
+    - Minimum tone on = 40ms
+    - Minimum tone off = 50ms
+    - Maximum digit rate = 10 per second
+    - Normal twist <= 8dB accepted
+    - Reverse twist <= 4dB accepted
+    - S/N >= 15dB will detect OK
+    - Attenuation <= 26dB will detect OK
+    - Frequency tolerance +- 1.5% will detect, +-3.5% will reject
+
+TODO:
+*/
+
+/*! \page dtmf_tx_page DTMF tone generation
+\section dtmf_tx_page_sec_1 What does it do?
+
+The DTMF tone generation module provides for the generation of the
+repertoire of 16 DTMF dual tones. 
+
+\section dtmf_tx_page_sec_2 How does it work?
+*/
+
+#define MAX_DTMF_DIGITS 128
+
+/*!
+    DTMF generator state descriptor. This defines the state of a single
+    working instance of a DTMF generator.
+*/
+typedef struct
+{
+    tone_gen_descriptor_t *tone_descriptors;
+    tone_gen_state_t tones;
+    char digits[MAX_DTMF_DIGITS + 1];
+    int current_sample;
+    size_t current_digits;
+} dtmf_tx_state_t;
+
+/*!
+    DTMF digit detector descriptor.
+*/
+typedef struct
+{
+    /*! Optional callback funcion to deliver received digits. */
+    void (*callback)(void *data, const char *digits, int len);
+    /*! An opaque pointer passed to the callback function. */
+    void *callback_data;
+    /*! Optional callback funcion to deliver real time digit state changes. */
+    void (*realtime_callback)(void *data, int signal);
+    /*! An opaque pointer passed to the real time callback function. */
+    void *realtime_callback_data;
+    /*! TRUE if dialtone should be filtered before processing */
+    int filter_dialtone;
+    /*! Maximum acceptable "normal" (lower bigger than higher) twist ratio */
+    float normal_twist;
+    /*! Maximum acceptable "reverse" (higher bigger than lower) twist ratio */
+    float reverse_twist;
+
+    /*! 350Hz filter state for the optional dialtone filter */
+    float z350_1;
+    float z350_2;
+    /*! 440Hz filter state for the optional dialtone filter */
+    float z440_1;
+    float z440_2;
+
+    /*! Tone detector working states */
+    goertzel_state_t row_out[4];
+    goertzel_state_t col_out[4];
+    /*! The accumlating total energy on the same period over which the Goertzels work. */
+    float energy;
+    /*! The result of the last tone analysis. */
+    uint8_t last_hit;
+    /*! The confirmed digit we are currently receiving */
+    uint8_t in_digit;
+    /*! The current sample number within a processing block. */
+    int current_sample;
+
+    /*! The received digits buffer. This is a NULL terminated string. */
+    char digits[MAX_DTMF_DIGITS + 1];
+    /*! The number of digits currently in the digit buffer. */
+    int current_digits;
+    /*! The number of digits which have been lost due to buffer overflows. */
+    int lost_digits;
+} dtmf_rx_state_t;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*! \brief Generate a buffer of DTMF tones.
+    \param s The DTMF generator context.
+    \param amp The buffer for the generated signal.
+    \param max_samples The required number of generated samples.
+    \return The number of samples actually generated. This may be less than 
+            samples if the input buffer empties. */
+int dtmf_tx(dtmf_tx_state_t *s, int16_t amp[], int max_samples);
+
+/*! \brief Put a string of digits in a DTMF generator's input buffer.
+    \param s The DTMF generator context.
+    \param digits The string of digits to be added.
+    \return The number of digits actually added. This may be less than the
+            length of the digit string, if the buffer fills up. */
+size_t dtmf_tx_put(dtmf_tx_state_t *s, const char *digits);
+
+/*! \brief Initialise a DTMF tone generator context.
+    \param s The DTMF generator context.
+    \return A pointer to the DTMF generator context. */
+dtmf_tx_state_t *dtmf_tx_init(dtmf_tx_state_t *s);
+
+/*! Set a optional realtime callback for a DTMF receiver context. This function
+    is called immediately a confirmed state change occurs in the received DTMF. It
+    is called with the ASCII value for a DTMF tone pair, or zero to indicate no tone
+    is being received.
+    \brief Set a realtime callback for a DTMF receiver context.
+    \param s The DTMF receiver context.
+    \param callback Callback routine used to report the start and end of digits.
+    \param user_data An opaque pointer which is associated with the context,
+           and supplied in callbacks. */
+void dtmf_rx_set_realtime_callback(dtmf_rx_state_t *s,
+                                   void (*callback)(void *user_data, int signal),
+                                   void *user_data);
+
+/*! \brief Adjust a DTMF receiver context.
+    \param s The DTMF receiver context.
+    \param filter_dialtone TRUE to enable filtering of dialtone, FALSE
+           to disable, < 0 to leave unchanged.
+    \param twist Acceptable twist, in dB. < 0 to leave unchanged.
+    \param reverse_twist Acceptable reverse twist, in dB. < 0 to leave unchanged. */
+void dtmf_rx_parms(dtmf_rx_state_t *s, int filter_dialtone, int twist, int reverse_twist);
+
+/*! Process a block of received DTMF audio samples.
+    \brief Process a block of received DTMF audio samples.
+    \param s The DTMF receiver context.
+    \param amp The audio sample buffer.
+    \param samples The number of samples in the buffer.
+    \return The number of samples unprocessed. */
+int dtmf_rx(dtmf_rx_state_t *s, const int16_t amp[], int samples);
+
+/*! \brief Get a string of digits from a DTMF receiver's output buffer.
+    \param s The DTMF receiver context.
+    \param digits The buffer for the received digits.
+    \param max The maximum  number of digits to be returned,
+    \return The number of digits actually returned. */
+size_t dtmf_rx_get(dtmf_rx_state_t *s, char *digits, int max);
+
+/*! \brief Initialise a DTMF receiver context.
+    \param s The DTMF receiver context.
+    \param callback An optional callback routine, used to report received digits. If
+           no callback routine is set, digits may be collected, using the dtmf_rx_get()
+           function.
+    \param user_data An opaque pointer which is associated with the context,
+           and supplied in callbacks.
+    \return A pointer to the DTMF receiver context. */
+dtmf_rx_state_t *dtmf_rx_init(dtmf_rx_state_t *s,
+                              void (*callback)(void *user_data, const char *digits, int len),
+                              void *user_data);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+/*- End of file ------------------------------------------------------------*/